A surprise Mythic+ affix has appeared on the PTR, Shielding periodically summons Orbs that shield nearby enemies if not destroyed! Interestingly, this affix was hinted at previously in Blizzard's Mythic+ Affix Feedback post last week as a potential change to Explosive, although today's Mythic+ Affixes Update left it out entirely — opting to replace Explosive with Volcanic instead. Given that change, it seems that Shielding is likely a work-in-progress and may not even be intended for inclusion in Season 2, although it appears to be available for testing from the Mythic+ Keystone Vendor on the PTR!
§ We are discussing a redesign for the Explosive affix to shift responsibility away from healers. Read more on wowhead.com